This invention relates in general to chewing gum compositions and, in particular, to the improvement comprising a food-grade shellac encapsulant for active chewing gum ingredients.
As is well-known in the art, chewing gum comprises a neutral and tasteless masticatory chewing gum base and one or more non-masticatory active ingredients mixed into the base. As used herein, an "active ingredient" is an ingredient such as a sweetener, a flavoring agent or a food-grade acid which determines flavor and taste characteristics of the gum; a body-treating ingredient such as a medicinal drug or pharmaceutical agent which is released at a gradual rate and ingested during chewing; or a breadth-freshening ingredient which treats or reduces oral malodor. In addition, the chewing gum may, and usually does, contain water-soluble and usually sweet non-masticatory bulking agents, a coloring agent and a plasticizing agent, the latter employed to improve the texture of the gum.
Certain active chewing gum ingredients benefit from or require encapsulation in order to achieve a gradual and controlled release of the ingredients during chewing or to promote their stability in chewing gum. For example, certain artificial sweeteners such as the dipeptide sweetener aspartame (L-aspartyl-L-phenylalanine methyl ester) have been found to be excellent sugar substitutes in chewing gum. However, the stability of artificial dipeptide sweeteners is a function of water activity, time, temperature and pH. Under unfavorable conditions, aspartame spontaneously converts to diketopiperazine with proportional loss of sweetness. Aspartame also degrades as the result of reactions with aldehydes present in certain flavors. In order to maintain the stability and sweetness of aspartame in chewing gum, it is necessary to reduce as far as possible the exposure of the aspartame to moisture, certain flavors and certain pH conditions.
Although the general technique of encapsulating ingredients is well-known, the prior art known to applicant does not teach satisfactory encapsulating agents for active chewing gum ingredients. For example, U.S. Pat. Nos. 4,122,195 and 4,139,639 discloses encapsulation of aspartame in Capsul dextrin and gum arabic. However, such encapsulants, which are hydrophilic and moisture-permeable, have been found to be of only limited effectiveness in preventing the degradation of aspartame in chewing gum.
While it would seem that hydrophobic encapsulating agents would provide better impermeability and gradual release characteristics than hydrophilic coatings, applicant is unaware of any hydrophobic coatings which have been successfully employed in the past for active chewing gum ingredients. Most hydrophobic materials which could be used as encapsulants, such as polyvinyl acetate, waxes and fats, are dissolved in the chewing gum base when they are mixed into the heated gum mass during the gum manufacturing process. Other hydrophobic materials such as high molecular weight polyvinyl acetate and styrene butadiene rubber are substantially insoluble in the food-grade solvents which are required in encapsulating processes. Applicant is unaware of any prior disclosure of hydrophobic encapsulating materials which have both of the necessary qualities of being insoluble in chewing gum base yet sufficiently soluble in the food-grade solvents used in encapsulating processes.